An article published on June 28, 2018, in the peer-reviewed Journal of Agricultural and Food Chemistry provides a review of the “state of present discussions” about the toxicological assessment of mineral oil hydrocarbons in foods. Koni Grob from the Official Food Control Authority of the Canton of Zurich, Zurich, Switzerland, reviews the existing assessments of mineral oil hydrocarbons (MOHs) and discusses the underlying assumptions and the limitations of the approaches chosen.

Among MOHs, saturated (MOSH) and aromatic (MOAH) types are distinguished for having differing toxicological endpoints and exposure levels. The main concerns about MOAH are genotoxicity and carcinogenicity, while MOAH-free MOSH (e.g., “white” purified mineral oils) were once considered “not fundamentally different from vegetable oils,” with food industry using these MOH “rather loosely.” However, there was “little justification for this,” Grob points out. The concerns about MOSH are their accumulation in human tissue along with granuloma formation, but also, often overlooked to date, increases in weight of several organs.

Grob summarizes and compares the assessments carried out by the European Scientific Committee on Food (SCF) in 1989, by the Joint Food and Agriculture Organization (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) in 1995, by JECFA in 2002, and by EFSA in 2012, along with the recommendations issued in 2017 by the German Federal Institute for Risk Assessment (BfR) in the context of MOH migration from recycled paperboard and printing inks (FPF reported). Most of the earlier assessments focused on differential toxicity of MOSH of different molecular mass ranges, while the BfR approach was “based on accumulation data.”

Grob observes that “extrapolation from animal tests grossly underestimates accumulation in human tissues,” due to “far longer lasting exposure” as well as “high absorption at a low dose” in humans. Furthermore, Grob explains that humans are mostly exposed to “predigested MOSH . . . from plants, meat, fish, eggs, and milk,” which “have a composition other than those applied in toxicity testing.” The important difference here is that “the propensity of predigested MOSH to accumulate could be higher by more than an order of magnitude.”

Regarding the toxicological endpoints, Grob suggests that “granuloma formation in livers might no longer be a relevant end point for MOSH toxicity.” Moreover, granuloma formation could be determined by “the composition of the oils tested,” rather than their molecular mass range. Therefore, instead of looking at granulomas, Grob calls for “address[ing] and further investigat[ing]” the increased organ weights. This effect was observed after MOSH exposure not only in Fischer 344 but also in Sprague Dawley rats. Grob concludes that, “because the weight increase is likely to be permanent, it might be more relevant than granuloma formation.”

Based on his analysis, Grob concludes that BfR’s assessment is “more prudent: exposure to strongly accumulated MOSH should be avoided.” Therefore, he suggests that “the evaluation(s) by SCF, JECFA, and EFSA should be replaced by the approach taken by the German BfR, starting from the accumulation observed in tissues.” This would result in acceptable daily intake (ADI) values for oils including MOSH C20-C40 being “far lower” than now. However, it might even “be preferable to phase out substantial use of mineral oils in food applications, including food contact materials, i.e., to abrogate approvals and ADIs,” Grob further states, adding that “industry factually largely phased it out anyway in recent years.”

With regard to mineral waxes, Grob notes that they “should be considered separately, provided that it can be confirmed that all constituents are readily degraded by human metabolism.”

Concerning the MOAH, Grob explains that genotoxicity is associated only with MOAH having three or more aromatic rings, while “no genotoxic mono- and diaromatic MOAH are known.” He further observes that “of MOAH detected in food, the dominant part has a single aromatic ring and a smaller part has two rings,” and “MOAH with three or more aromatic rings usually constitute a small part.” However, a limit may be required for MOAH with at least three aromatic rings. However, since the content of such species in MOAH mixes is so low, and, furthermore, “no MOH found in food contain more than 30% MOAH,” Grob concludes that “no limit [for MOAH] might be needed if the limit for MOSH is low.”

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